Personal cleansing compositions including facial cleansers, while good at removing sebum and grime from the skin and hair, may cause skin irritation and, or damage to the surfaces being cleansed. Personal cleansing compositions are typically detersive in nature, meaning that they performing a cleaning function, and often have an acidic pH (below 7). Further, formulations containing lower amounts of active ingredients (such as detersive surfactants) with sufficient cleansing and conditioning benefits can be desirable. The addition of suspended particles and, or droplets of materials such as oils or petrolatum has been attempted in order to provide cleansing and conditioning benefits. See U.S. Patent Publ. No. 2005/0201965.
Releveling of active ingredients has made suspension particles an attractive technology to maintain performance benefits but the reduction of actives results in changes to the rheology of the compositions as many active ingredients provide some degree of rheology modification (such as shear thickening and particle suspension capabilities). Ingredients which provide a functional benefit, such as cleaning or conditioning, and impact rheology are referred to as “internal structurants.”
Attempts to introduce structuring agents into various detersive compositions have been described. Known external structuring agents include polymers or gums, many of which are known to swell or expand when hydrated to form random dispersion of independent microgel particles. Examples of polymers and gums include: gellan gum, pectine, alginate, arabinogalactan, caageenan, xanthum gum, guar gum, rhamsan gum, furcellaran gum, carboxymethylcellulose and cellulose. See e.g. U.S. Pat. No. 6,258,771 to Hsu et al. U.S. Pat. No. 6,077,816 to Puvvada et al.; and WO 2006/116099 to Fleckenstein et al. These polymer or gum structurants are typically needed at relatively high levels which have been found to leave certain compositions opaque and cloudy in appearance. Further, certain suspension polymers, such as acrylate cross-linked acid copolymers such as disclosed in“Polymer For Personal Care, Carbopol EDT® Resins: Formulation Tips”, March 1994 by Noveon™, Inc. have been described (disclosing the use of polyol, such as glycerin or polyethylene glycol). Many of these suspension polymers, however, have been found by consumers to feel slimy and/or do not rinse easily off after use. This is particularly undesirable for personal cleansing compositions as they are used on the body where consumer hand feel is important.
The addition of certain structurants which are believed to form fibrous networks have been described as providing desirable rheological modification benefits without composition opacity. See U.S. Patent Publ. No. 2008/108714 A1 (disclosing microfibrous cellulose for use in various detergent compositions and U.S. Patent Publ. No. 2005/203213 A1 (disclosing the use of non-polymeric crystalline hydroxyl-functional materials and polymeric structurants such as polyacrylates, polysaccharides, and polymer gums). These and other structuring agents can be referred to as “external structurants” as they are added primarily for rheology modification purposes and not for an active benefit such as cleaning, conditioning, or fragrance.
It has been found, however, that microfibrous celluloses alone fail to provide sufficient rheological benefits for certain personal care compositions, such as those with low levels of internal structurants and/or acidic pH, or where high levels of or very large/dense particulates are desired, such as in scrubs or facial cleansers. Further, there is a need for structuring systems which are less susceptible to the negative side effects observed with some known structuring systems, such as causing compositional opacity and filmy or slimy feel during use.